1. Field of the Invention
The present invention relates to a resonator employing a piezoelectric ceramic resonator, and particularly relates to a resonator having excellent free-fall resistance.
2. Description of the Related Art
Piezoelectric resonating parts (resonators) which employ a piezoelectric ceramic resonator are known as resonators that attain an oscillating frequency. As illustrated in FIG. 1, a piezoelectric ceramic resonator 2 is constituted by forming a pair of vibrating electrodes 22, 23 on the front and back main faces of a polarized piezoelectric ceramic substrate 21, so that vibrations are trapped in the vicinity of the pair of vibrating electrodes 22, 23. As illustrated in FIG. 2, a resonator 1 employing this piezoelectric ceramic resonator 2 comprises a substrate 3 and a cap 5. The substrate 3 has a strengthening function, and for example can be constituted from a ceramic such as steatite (MgO.SiO2), alumina (Al2O3) or the like. Such a substrate normally has a thickness of about 0.05 to 0.7 mm. Terminal electrodes 31, 32 are formed on the front and back faces of the substrate 3. The substrate 3 can also be constituted using a single-layer dielectric ceramic, a ceramic laminate or the like, so as to combine dielectric function with a strengthening function. Examples of a single-layer dielectric ceramic include compounds having barium titanate as a main component. Examples of a ceramic laminate include low-temperature sintered ceramics having internal electrodes, and can be obtained by, for example, simultaneously sintering Al2O3 or CaZrO3 to which a glass component has been added with a conductive paste of Cu, Ag or the like, at a temperature of 1,000° C. or less.
The piezoelectric ceramic resonator 2 is adhered and fixed onto the terminal electrodes 31, 32 by a conductive stator 4, such as a conductive resin or solder, which combines the functions of conduction and adherence. A constant vibration space can be secured according to the thickness of the conductive stator 4 in between the piezoelectric ceramic resonator 2 and substrate 3.
The cap 5 is adhered onto the substrate 3 by an adhesive, for example, so as to cover the piezoelectric ceramic resonator 2. Although the cap 5 can be constituted from a ceramic such as steatite (MgO.SiO2), alumina (Al2O3) or the like as in the case of the substrate 3, it is also acceptable to constitute from an alloy or similar metal. The thickness of the cap 5 can be made about the same as that of the substrate 3.
A resonator 1 such as that described above is disclosed in, for example, Japanese Patent Laid-Open No. 8-237066 (Patent Document 1).